000
FXUS63 KTOP 041742
AFDTOP
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1142 AM CST Sun Dec 4 2016
...Update to aviation forecast discussion...
.SHORT TERM...(Today and tonight)
Issued at 356 AM CST Sun Dec 4 2016
Mid/upper level trough responsible for the band of rain is currently
moving over central KS. This wave is forecasted to move eastward
this morning along with the rain. The rain should begin to exit the
area around or shortly after sunrise with additional amounts of
0.25" expected. Significant dry mid level air will move in from the
northwest behind the wave. Models are suggesting that fog will
develop behind the rain mainly across north central KS. There is a
chance the fog could be dense in some locations especially where the
snow fell yesterday. Later this morning the visibility should
improve with daytime mixing. Again the fog may linger slightly
longer in locations with snow on the ground. Clouds should also
clear out later today with highs in the mid to upper 40s. The
temperatures may stay in the lower 40s where there is snow on the
ground. Southerly flow develops tonight as flow aloft becomes more
zonal and a shortwave tracks over the northern Rockies. Lows tonight
should drop into the upper 20s with mostly clear skies. The
southerly winds should prevent strong radiational cooling and the
development of fog as suggested by some of the model guidance.
Perhaps some shallow ground fog could not be ruled out especially
since we just had widespread rainfall.
.LONG TERM...(Monday through Saturday)
Issued at 356 AM CST Sun Dec 4 2016
By Monday morning, a mid-level trough and area of surface low
pressure will be situated near the High Plains region, with a decent
pressure gradient setting up over the CWA. As a result, breezy
southerly winds will push temperatures above the seasonal normals
with highs in the low/mid 50s. This trough will stay north of the
area as it tracks eastward Monday night through Tuesday, but will
help to push the cold front through the CWA Monday night. Models
show a closed low over Texas on Monday lifting northeastward and
merging into the mid-level trough. While this southern wave will
moisture northward, models are keeping precipitation just southeast
of the CWA so have a dry forecast. Breezy northerly winds behind the
frontal passage on Tuesday will result in much cooler air being
ushering into the area with high temperatures plunging into the 30s.
The next mid-level trough is expected to move into the Pacific
Northwest early Tuesday morning and deepen across the northern
Rockies before advancing into the central U.S. mid-week. While
models are generally in decent agreement with the timing of the
onset of precipitation, there are model discrepancies with
accumulation amounts and when precipitation will end. The 00z GFS
has limited QPF amounts and is more progressive with the trough
progressing east of the area, limiting precipitation chances to just
the daytime hours on Wed. The ECMWF is slower with the system, thus
keeping precipitation chances into Wednesday evening. Also, the
ECMWF has much higher QPF amounts compared to the GFS. With
temperatures looking to be cool enough to keep precipitation type
entirely as snow, these differing QPF amounts have a significant
impact on potential snow accumulation across the region. Either way,
a few inches of snow in some locations will be possible with this
system on Wednesday.
In addition to the snow chances, this system will also bring push of
cold air into the region, with high temperatures plunging into the
20s for Wednesday and Thursday and lows into the teens and single
digits. These temperatures combined with light winds will cause
wind chill values to drop into the negative single digits for most
locations. Conditions will warm up slightly Friday into Saturday as
surface high pressure shifts southeast of the area, with highs
rising back into the 30s. Models show another shortwave skimming
across the area next weekend, however there are significant
differences in the timing of precipitation and temperatures around
freezing. As a result, cannot rule out the potential for mixed
precipitation.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1141 AM CST Sun Dec 4 2016
LIFR/IFR cigs will gradually become vfr by 20Z to 21Z time period
as stratus moves southeast across the area. Winds generally from
the west around 10kts. Added some mvfr vsbys tonight after 09Z at
TOP and FOE which could briefly lower to IFR at TOP near 12Z.
WInds increase from the south on Monday after 15Z to 10-15kts with
some higher gusts at MHK.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Sanders
LONG TERM...Hennecke
AVIATION...53